1. Field of the Invention
This invention relates to (1) a process for improving nozzles extending substantially vertically through openings in the head of a nuclear reactor and which are circumferentially welded to said head through a weld lying on an inner surface of said head and the outer surface of said nozzle immediately adjacent thereto which comprises forming a coaxial, circumferential groove extending upwardly into at least a portion of said nozzle extending into said reactor and thereafter filling said circumferential groove with a weld material and (2) to a nuclear reactor head carrying said nozzles.
2. Description of the Prior Art
Nuclear reactors are normally provided with a head having nozzles extending substantially vertically through openings therein and which are circumferentially welded to said head through a weld lying on an inner surface of said head and on the outer surface of said nozzle immediately adjacent thereto. These nozzles, generally made of an Inconel alloy, such as Inconel 600, provide for passage therethrough of control rod drive shafts attached to an exterior control rod drive mechanism. Tensile stresses generated from the weld holding the nozzle to the nuclear reactor head tend to facilitate stress crack formation in the inner surface of the nozzle in the vicinity of said weld. These cracks, in time, can extend upwardly into the body of the nozzle or into a portion of the weld, or both, into communication with the outer surface of the nozzle above the weld, into the space between the outer surface of the nozzle and the adjacent surface of the head opening, and then to the exterior of the reactor. Irradiated water can thus pass outwardly into the atmosphere, creating a serious pollution problem. If such cracks are circumferential, the nozzle can be detached from the reactor head by the pressure in the reactor, also with damaging results.
I have found that such problems in the nozzle arising from the formation of cracks therein can be obviated by forming a coaxial circumferential groove extending upwardly into at least a portion of the nozzle that extends into the reactor and then filling such circumferential groove with a weld material.